This invention relates to pressure-sensitive record material sheets. More particularly, the invention is directed toward pressure-sensitive record material containing a urea-formaldehyde resin pigment as a substitute for all or a part of the usual pigmentary coating on the acid-reactive surface.
Many attempts have been made in the prior art to whiten the surface of pressure-sensitive record sheets while also improving the intensity of the dye images formed. Coatings of a white pigment such as CaCO.sub.3 (chalk) are conventionally employed in the art. Acid-reactant pigments such as various clays, zeolites and colloidal silica have also been used in record sheets for many years. Such record sheets, when placed in contiguous relationship with a transfer sheet surface containing microscopic rupturable capsules of a colorless chromogeneous material, produce an image under pressure which causes the capsules to break, whereby some of the colorless chromogeneous material is transformed to the acidic pigment coating where it reacts to give a colored mark.
U.S. Pat. No. 3,617,410 of Clark describes pressure-sensitive record sheets having improved resistance to smudging wherein the conventional acidic pigments employed are replaced by high-bulking pigments which are substantially non-reactive with the basic dyes in the colorless marking ink, such as hydrated alumina, high-bulking filler clay and talc pigments. While providing satisfactory print intensity, such record material has other disadvantages.
One of the objects of the present invention is to provide pressure-sensitive record material having a greatly improved image intensity.
Another object of the invention is to provide pressure-sensitive record material having a very high print speed, i.e., the rate at which full color intensity is realized when acid-reacting sheets are treated with oil solutions of base-reacting chromogens.
Still another object of the invention is to provide pressure-sensitive record sheets having an excellent contrast between the white background of the image-bearing surface and the resulting image itself.
These and other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following specification and claims.